Smoking articles

ABSTRACT

A smoking article comprising a smoking rod, a filter and ventilation means incorporated in the filter and communicating with the outside of the smoking article, viscous fluid in the ventilation means closing or partially closing the ventilation means, the viscous fluid being displaceable during use of the smoking article enabling ventilation to occur.

This invention relates to smoking articles and particularly but notexclusively to filter cigarettes.

Smokers of cigarettes have varying tastes and preferences. Within thepopulation of smokers there are various groups such as those who preferlow tar and those who prefer higher tar. They all choose theirparticular brands and smoke them as they wish. There are, however,extreme cases such as those who buy one brand of filter cigarette butprior to smoking detach the filter. Others smoke low tar cigarettes butin an unusual fashion in that the filter is placed well into the mouththereby blocking the vents with the lips. Others prefer middle tarcigarettes and may only smoke the first half.

Cigarettes ate commonly ranked according to their tar delivery which isevaluated by machine smoking at predetermined puff volume, duration ofpuff and interval between puffs. Smokers, however, perform their habitas they please and a cigarette that does not readily conform to theirsmoking pattern is deemed poor whilst a cigarette that conforms to theirwishes is satisfying.

According to the present invention there is provided a smoking articlecomprising a smokable rod and ventilation means whereby, in use, thepuffing characteristics of the smoker determine the amount ofventilation given by the ventilation means, the ventilation means beinginitially closed or partially closed by a viscous fluid.

It will be appreciated that the term `viscous fluid` not only includesliquids but also materials that are "plastic" in that they aredeformable or displaceable by means of a pressure differential withoutreturning to their original shape after the pressure differential isremoved. The term, therefore, includes gels, petroleum jellies, greaseetc.

The ventilation means may be incorporated into a filter. The filter mayhave conventional ventilization besides the ventilation means described.The ventilation means when acted upon during puffing reacts andcontinues to react during subsequent puffs in a manner dependent uponthe puffing characteristics employed until it intervenes enabling anincrease in ventilation.

The ventilation means preferably continues to react to the puffingwhereby the ventilation continues to increase towards a maximum. Thesmoking article has an inherent lower delivery not manifest at the startof smoking. This manifestation is realised once the smoker has exertedsufficient demands upon the smoking article and his want is somewhatsatiated.

Commonly the ventilation means will include a system of vents in theperiphery of the filter.

In one arrangement the viscous fluid disposed in one or more tubes, saidone or more vents communicating only with said one or more tubes.Conveniently said one or more tubes have ends of wider bore towards theair entry end to prevent capillary loss of the viscous fluid.

In another arrangement the viscous fluid is disposed in one or morechannels located in the periphery of the ventilation means, said one ormore vents communicating only with said one or more channels.

The tubes or channels may have varying cross-sections along theirlongitudinal axis.

Means may be provided around the fluid exit end of the channels or tubesto assist the removal of viscous fluid, This removal means may comprisean absorbent material, tube, or tubes, slit or slits to wick away thefluid. The tubes may be concentric, in line or at an angle to the fluidtube.

The removal means is so positioned such that capillary loss by surfacetension does not operate until the viscous fluid has been expressed bythe action of puffing.

In a further arrangement the viscous liquid is disposed in an open endedtube which has a smaller internal cross sectional area towards the airentry end. Preferably the tube is conical.

Preferably the viscous fluid in the channels or tubes has a viscosity ofbetween 0.01 Poise and 1000 Poise (0.01 Stokes and 1000 Stokes). Onesuitable fluid is glycerol and others includes syrups like sugar inwater as well as vegetable and mineral oils. The channels or tubes mayalso contain particles and/or fibres.

With the above described smoking articles the ventilation is low or zeroat the start of smoking whereby the articles readily conform to thedemands of smokers whilst, dependent upon the smoker's puffingcharacteristics, later the articles ventilate thereby allowing thesmokers to continue puffing as previously without exceeding their need.Furthermore, compared to conventional smoking articles, the range oftotal tar deliveries, obtainable with puff volume, is much smallerthereby limiting the total tar a smoker may obtain; the deliveries perpuff are more uniform and the pressure drop decreases over the smokingperiod.

Conventional cigarettes, when machine smoked, generally give anincreasing yield of tar with puffing, for example:

For a smoking regime of 2 second puff duration and a frequency of onepuff per minute with the given puff volumes the following data wasobtained:

    ______________________________________                                                  TPM (mg) deliveries at                                              Puff      given Puff Volumes                                                  Number    25 ml        35 ml   50 ml                                          ______________________________________                                        1         0.51         1.04    1.27                                           2         0.47         0.93    1.23                                           3         0.50         1.08    1.50                                           4         0.60         1.07    1.58                                           5         0.66         1.13    1.63                                           6         0.77         1.28    1.75                                           7         0.89         1.31    1.99                                           8         0.94         1.60    2.10                                           9         0.96         1.59    2.83                                           10        1.00         2.01                                                   Total Tar 7.30         13.04   15.88                                          ______________________________________                                    

The ventilation (%) and Pressure Drop data with Puff Number is givenbelow:

(where Pressure Drop (PD) mm H20 is the maximum over the puff)

    ______________________________________                                               Puff Volume                                                                   25 ml     35 ml       50 ml                                            Puff     Vent   PD       Vent PD     Vent PD                                  No.      %      mm       %    mm     %    mm                                  ______________________________________                                        1        24.1   160      34.0 177    32.0 257                                 2        24.3   154      35.0 180    31.0 261                                 3        23.5   164      33.5 179    32.5 261                                 4        22.5   162      32.4 175    28.8 259                                 5        25.4   160      30.0 173    30.0 261                                 6        25.5   153      31.0 173    30.8 257                                 7        22.0   151      29.9 169    28.8 264                                 8        22.2   153      29.8 175    32.8 272                                 9        21.1   152      31.7 178    30.8 266                                 10       22.2   157      28.9 176                                             ______________________________________                                    

The tar yield profile results in the strength of the cigaretteincreasing considerably during smoking. Obviously, if the initialstrength is acceptable to the smoker then it will become stronger andless acceptable during smoking and the converse will also be true i.e.if the final strength is acceptable then the cigarette is initially toomild.

The present invention reduces or eliminates the yield profile so that ifthe initial delivery is acceptable then it will remain so throughout thesmoking of the cigarette.

Our arrangements also allow a smoker to conform the cigarette, by theaction of puffing, to their needs without the problem of too muchdiluting air. Once their early desire is satiated their want oftendeclines and so, depending on their early demands, sooner or later theventilation increases thereby allowing a consistent delivery as to need.

Alternatively the smoker can puff on an unlit cigarette so as to openthe ventilation prior to lighting up.

Smoking articles and particularly cigarettes have an inherent litresistance. The energy utilised in puffing to obtain sufficient smoke isessentially the product of the volume and pressure drop created. Thepressure drop created is the product of the flow rate and litresistance. High resistance, `high pressure drop` cigarettes requiremore energy by the smoker to achieve the same puff volume. Ourarrangements allow the energy used in puffing to be partitioned betweenthe generation of smoke and work done on the ventilation means. Thispartition is very much in favour of smoke generation. Air is allowedthrough once sufficient partitioned energy has been used to open theventilation means. The energy required is dependent upon the dimensionsof the ventilation means, the fluid used and the puffing characteristicsof the smoker.

The preferred ventilation means consists of air vents, a fluid blockedtube and a receiving system to remove the fluid expressed oversuccessive puffs. The chosen smoking article e.g. a cigarette wouldrequire a minimum ventilation at the outset of puffing and a maximumventilation after sufficient puffs to express the fluid from the tube.The minimum ventilation can be supplied using conventional means. Asimple resistance model may be used to estimate the required resistanceto air flow of the empty fluid tube. Once the resistance to air flow ofthe empty fluid tube is known the dimensions of the tube may beestimated from the Poiseuille equation. These dimensions are not uniquebut the length of tube and radius of the bore are related. The tube boreand length need to comply with the requirements necessary to hold thefluid by surface tension. These requirements must fulfil the conditionthat the fluid is not expressed prior to smoking i.e. the fluid must notempty under gravitational pull or expression due to rates of change ofmomentum.

The fluid fill is chosen with regard to its viscosity given the possibletube dimensions consistent with the maximum ventilation and surfacetension requirements. A first estimate as to the required viscosity maybe obtained from the Poiseuille equation where consideration is given tothe fact that the tube is emptying. In practice the fluid viscosity ischanged if the estimated viscosity does not achieve the requiredoperating characteristics as to ventilation. The fluid must not emptytoo quickly or too slowly under a given series of puffs (the pressuredrop being dependent on the lit resistance). For each puff the fluidexpressed needs to come under the influence of the removal means suchthat at least some of the fluid expressed is removed. After sufficientpuffs the tube opens allowing some ventilation through the means andover further puffs the ventilation increases towards the maximum.

An example according to the present invention is given in FIGS. 8 and 9which show the construction and dimensions of the ventilation means. Inthis example the tube containing the fluid of viscosity 125 Poise (125Stokes) and the collection tubes were fashioned from a single piece ofpolyethylene tube. The ventilation means was attached to a conventionalfilter cigarette. The tar yields with puffing are given below.

For a smoking regime of 2 second puff duration and frequency one puffper minute with the given puff volumes, the following data was obtained:

    ______________________________________                                                  TPM (mg) deliveries at                                              Puff      given Puff Volumes                                                  Number    25 ml        35 ml   50 ml                                          ______________________________________                                        1         0.64         1.06    1.11                                           2         0.66         0.92    1.06                                           3         0.79         0.81    1.06                                           4         0.96         0.75    0.96                                           5         0.99         0.79    0.95                                           6         1.01         0.77    1.08                                           7         1.05         0.82    1.01                                           8         0.96         0.80    1.09                                           9         1.02         0.81    1.07                                           10        0.98         0.82    1.07                                           Total Tar 9.06         8.35    10.46                                          ______________________________________                                    

The ventilation (%) and Pressure Drop data with Puff Number is givenbelow:

(where Pressure Drop (PD) mm H20 is the maximum over the puff)

    ______________________________________                                               Puff Volume                                                                   25 ml     35 ml       50 ml                                            Puff     Vent   PD       Vent PD     Vent PD                                  No.      %      mm       %    mm     %    mm                                  ______________________________________                                        1        0      147      0    221     7.0 318                                 2        0      158      0    207    25.0 233                                 3        0      157      14.7 161    28.4 236                                 4        0      159      22.6 133    30.0 181                                 5        0      154      29.2 137    33.3 174                                 6        0      146      33.9 115    37.5 160                                 7        0      143      36.8 115    46.2 176                                 8        21.0   145      36.2 116    38.2 161                                 9        31.2   142      40.8 111    39.8 153                                 10       38.4   145      42.2 123    45.8 151                                 ______________________________________                                    

Embodiments of the present invention will now be described in moredetail. The description makes reference to the accompanying diagrammaticdrawings in which:

FIG. 1 is a lengthwise cross-section through a cigarette according tothe present invention,

FIG. 2 is a lengthwise cross-section at 90° to the section in FIG. 1,

FIG. 3 is a lengthwise section through a second embodiment of smokingarticle according to the present invention,

FIG. 4 is a lengthwise section through a third embodiment of smokingarticle according to the present invention,

FIGS. 5A, 5B and 5C are lengthwise sections through a further embodimentof tube for use in a smoking article according to the present invention,

FIGS. 6A, 6B and 6C are lengthwise sections through a still furtherembodiment of tube,

FIGS. 7A, B, C and D are lengthwise sections through another embodimentof tube,

FIG. 8 shows a perspective view of the components of a still furtherembodiment,

FIG. 9 shows a cut away perspective view of the FIG. 8 components inassembled form, and

FIG. 10 shows a part assembled perspective view and an exploded view ofa yet further embodiment.

In FIGS. 1 and 2 there is shown a smoking article 10 comprising asmokable tobacco rod 11, or other flavour delivery systems attached to afilter 12 by means of conventional tipping paper 13. The filter 12 andthe paper 13 incorporate ventilation means in the form of perforations14 in the paper 13 communicating only with a circumferential groove 15in the filter 12 which groove incorporates a diametrical through passage16 which in turn communicates with a tube 17. The tube 17 extendslengthways of the filter 12 towards the mouth end 18 of the smokingarticle 10 and contains a quantity of viscous fluid 19. The tube 17 hasend 20 of enlarged bore so as to prevent loss of the viscous fluid 19 bycapillary action, the surface tension of the fluid 19 keeping it in thetube. Clearly, the larger the bore the shorter the length of fluid thatcan be held by the surface tension. Also, as fluid is expressed, theviscous resistance of the remainder is reduced as there is less fluidpresent. These considerations have to be taken into account duringdesign.

The fluid 19 effectively blocks air from being drawn through theperforations 14, through the passage 16, down the tube 17 towards themouth of the smoker. The viscous fluid 19 is confined such that when asmoker puffs the cigarette the fluid is expressed to a greater or lesserdegree depending on the strength of draw by the smoker. Once sufficientdraws have been taken such that viscous fluid has been expressed, an airway is formed and ventilation takes place. Full ventilation takes placeonce the maximum amount of viscous fluid has been expressed. In practisethere will probably still be a coating of fluid in the tube 17.

One preferred viscous fluid 19 is glycerol which has a viscosity ofaround 10 Poise. Air's viscosity is about 1.8×10⁻⁴ Poise. It isenvisaged that any viscous fluids could be used, although preferably inthe range 0.01 Poise to 1000 Poise.

By way of example, a cigarette constructed similarly to the FIG. 1 and 2arrangement of 0.004 cm³ capacity and length 1.9 cm filled with glycerolwas observed on machine smoking to have the following dilution:

    __________________________________________________________________________    Puff No                                                                              1 2 3 4 5 6 7 8 9 10                                                                              11                                                                              12                                                                              13                                                                              14                                                                              15                                         __________________________________________________________________________    Dilution %                                                                           0 0 3 8 11                                                                              12                                                                              15                                                                              16                                                                              18                                                                              19                                                                              21                                                                              23                                                                              22                                                                              22                                                                              22                                         __________________________________________________________________________

It will be appreciated that more than one tube 17 can be employed.Similarly a prototype had two tubes containing glycerol, each tubeextending sideways out of the filter so that the movement of fluid 19could be observed. On puffing, with glycerol in the tubes the followingdata was observed:

    __________________________________________________________________________    Puff No                                                                             1 2 3 4 5 6 7 8 9 10                                                                              11                                                                              12                                                                              13                                                                              14                                                                              15                                                                              16                                        __________________________________________________________________________    Dilution %                                                                          0 0 0 0 0 0 0 3 3 12                                                                              11                                                                              8 10                                                                              17                                                                              27                                                                              30                                        __________________________________________________________________________

Other arrangements are of course possible. One of these is shown in FIG.3 where the viscous fluid 19 is disposed in lengthwise extendingchannels 21 formed in the filter 12. The tipping paper 13 closes off thechannel 21 so that a tube is effectively created. Again the perforations14 communicate only with the channels. Any number of channels could beprovided.

FIG. 4 shows an arrangement similar to that shown in FIGS. 1 and 2 butthe tube 17 also contains particles and/or fibres around which is theviscous fluid. The particles/fibres act as packing in the flow tube 17and will require a tube 17 of wider bore. The particles/fibres act as aseries of small channels through which the viscous fluid is drawn whenthe arrangement is puffed. Once the fluid is expressed from the tube 17air will be able to flow between the particles/fibres.

FIGS. 5A, 5B and 5C show a simple tube 17 which is surrounded by aporous absorbent filter material 25. FIG. 5A shows the arrangementbefore puffing. It will of course be appreciated that the tube 17 inFIG. 5A would in use be assembled within the filter in a similar mannerto the tube 17 in FIGS. 1 and 2. The surface tension of the viscousfluid 19 retains the fluid 19 in the tube 17 whatever its orientation.

After a number of puffs, as depicted in FIG. 5B, the fluid is drawn outof the mouth end of the tube somewhat. There is, however, the tendencyfor the fluid to flow back into the tube between puffs due to surfacetension effects. However the presence of the absorbent material 25overcomes these effects and the viscous fluid 19 is wicked away from thetube 17 each time the smoking article is puffed. After a time the tubebecomes unblocked.

It will of course be appreciated that the tube 17 does not necessarilyempty itself of the viscous fluid. It is also clear that the use ofabsorbent material could also be applied to channel type arrangementexemplarised by FIG. 3.

Another example of a technique to help the removal of the viscous fluid19 from the tube 17 is shown in FIGS. 6A, B and C. A second tube 26 isarranged outside the tube 17 in a concentric manner. Only the inner tube17 communicates with ventilation perforations in the filter.

Again, as the device is puffed the viscous fluid is drawn out of themouth end of the tube. The surface tension effects ensure that the fluid19 is drawn into the annular space between tubes 17, 26 so as toprogressively unblock tube 17 on further puffs.

Highly viscous liquids can be used in conjunction with relatively widebores. For example, some viscous materials are displaced upon puffing,but do not fully recover (due to surface tension) between puffs.Subsequent puffs increase the displacement of the viscous material untilfinally there is breakthrough leaving the material coating the inside ofthe tube.

It has been found that an open ended conical tube is particularlysuitable in such an arrangement as shown in FIG. 7. The narrow end 28communicates with the ventilation holes 14. The viscous material 19 isdisposed in the tube and surface tension urges the material towards thesmall bore of the cone. It will be appreciated that the cone angle andbore sizes will determine the maximum amount of material that can beretained by surface tension such that gravity is overcome in allorientations of the tube 19.

FIGS. 7A, B, C and D illustrate the operation of the conical tubeoutlined above. FIG. 7A shows the arrangement before puffing, FIG. 7Bshows the displacement of the viscous material 19 during the first puffand FIG. 7C shows the slight recovery of the viscous material 19 in thedwell between puffs. FIG. 7D shows the arrangement at the breakthroughpuff and it will be seen that the viscous material 19 has not left thetube but forms a coating along a length of the tube wall.

The displacement effect and the final breakthrough are accentuated usinga conical tube, but other effects can be obtained as desired using tubesof other shapes and sections. In one envisaged arrangement a capillaryfunnel is provided. The funnel comprising a capillary tube communicatingwith the ventilation means at one end and a conical tube similar to thatin FIG. 7 at the other end.

Another example uses `plastic` materials which change shape under loadwithout returning to their original shape after the load is removed.Such a property has advantages in that there is no tendency for thematerial to be drawn back into the tube in the dwell between puffs.Vaseline is an example of such a material having such properties.

In FIGS. 8 and 9 there is shown a tubular insert 40 having an externaldiameter similar to that of the smoking article in which it is to beincorporated. An aperture 41 is provided in one side of the insert 40. Atube 42 is cut partway along its length and cut sideways to allow thetwo leg portions 43 to be bent back through 90° so as to produce aT-shaped element 44. This element is secured inside the insert 40 withthe uncut end of the tube communicating with the aperture 41. Theoutwardly facing edges of the leg portions 43 abut the inside of theinsert 40 opposite the aperture 41. A predetermined quantity of viscousfluid 19 is introduced into the uncut portion of the tube 42. The insertcan then be incorporated in a cigarette. The aperture 41 will only beopened after the viscous fluid is drawn out of the tube 42 by the actionof puffing, the viscous fluid being drawn initially into collectionareas defined between the legs 43 and the insert 40.

In FIG. 10 there is shown a perspective view of a two piece injectionmoulding and the components in assembled form. The moulding replicatesthe description given in FIGS. 8 and 9 where the dimensions of the fluidfilled tube and its crucial positional relationship to the receivingsystem to remove the fluid are the same. Further the moulding,enumerated as FIGS. 1 and 2, include a circumferential groove 15 wherein this case it is inappropriate to include the whole circumference.FIG. 10 shows the assembled moulding and its relationship withconventional cigarette construction materials. The perforations 14 inthe paper 13 communicating with the circumferential groove in themoulding complete the ventilation means. Conventional ventilation isalso depicted as a single row of perforations. The minimum ventilationbeing provided by the conventional means and the maximum ventilationprovided by both the conventional means and the so described ventilationmeans.

The ventilation means, fluid and filter may be biodegradable to allowthe consumer to dispose of the butts without environmental problems.

Although the invention has been described mainly with respect tocigarettes, it could be applied to any other smoking article includingcigars, pipes etc.

I claim:
 1. A smoking article comprising a smokable rod and aventilation means located within said smokable article and communicatingwith the outside of said article, viscous fluid in said ventilationmeans closing or partially closing said ventilation means, said viscousfluid being displaceable during use of said smoking article enablingventilation to occur.
 2. A smoking article as claimed in claim 1 whereinthe viscous fluid has a viscosity of between 0.01 Poise (0.01 Stokes)and 1000 Poise (1000 Stokes).
 3. A smoking article as claimed in claim 1wherein the viscous material is plastic deformable under load withoutreturning to its original shape after the load is removed.
 4. A smokingarticle as claimed in claim 1 wherein the ventilation means isbiodegradable.
 5. A smoking article comprising a smoking rod, a filterand ventilation means incorporated in said filter and communicating withthe outside of said smoking article, viscous fluid in said ventilationmeans closing or partially closing said ventilation means, said viscousfluid being displaceable during use of said smoking article enablingventilation to occur.
 6. A smoking article as claimed in claims 1 and 5wherein the ventilation means includes vents in the periphery of thesmoking article.
 7. A smoking article as claimed in claim 6 wherein theventilation means is comprised of one or more tubes or one or morechannels located in the periphery of the ventilation means.
 8. A smokingarticle as claimed in claim 7 wherein the ventilation means is comprisedof one or more tubes.
 9. A smoking article as claimed in claim 8 whereinthe viscous fluid is disposed in one or more of said tubes.
 10. Asmoking article as claimed in claim 9 wherein the tubes vary incross-section along their length.
 11. A smoking article as claimed inclaim 8 wherein said one or more tubes are open-ended and have a largerinternal cross-sectional area towards the lower pressure end of theuser's end of the said smoking article.
 12. A smoking article as claimedin claim 11 wherein the tube or tubes are conical.
 13. A smoking articleas claimed in claim 7 wherein the ventilation means is comprised of oneor more channels located in the periphery of the ventilation means. 14.A smoking article as claimed in claim 13 wherein the viscous fluid isdisposed in one or more of said channels.
 15. A smoking article asclaimed in claim 7 wherein removal means are provided around the fluidexit end of the channels or tubes to assist the removal of viscousfluid.
 16. A smoking article as claimed in claim 15 wherein the removalmeans comprises an absorbent material to wick away the fluid.
 17. Asmoking article as claimed in claim 15 wherein the removal meanscomprises slits, channels or tubes.
 18. A smoking article as claimed inclaim 15 wherein the removable means comprises an outer concentricchannel or tube.
 19. A smoking article as claimed in claim 7 wherein thechannels or tubes contain particles and/or fibers.
 20. A filter for asmoking article comprising a filter and ventilation means incorporatedin said filter and communicating with the outside of said filter, saidventilation means containing a viscous fluid closing or partiallyclosing said ventilation means, said viscous fluid being displaceableduring use of said filter with a smokable rod.
 21. A filter as claimedin claim 20 wherein the ventilation means is comprised of one or moretubes.
 22. A filter as claimed in claim 20 wherein the ventilation meansis comprised of one or more channels located in the periphery of theventilation means.
 23. A filter as claimed in claim 22 wherein the tubeor tubes are open-ended and have a larger internal cross-sectional areatowards one end of the filter.
 24. A filter as claimed in claim 21 orclaim 22 wherein the channels and tubes also contain particles and/orfibers.
 25. A filter as claimed in claim 20 wherein the ventilationmeans incorporates vents in the periphery of the filter.
 26. A filter asclaimed in claim 25 wherein said vents communicate only with one or moretubes in which said viscous fluid is disposed.
 27. A filter as claimedin claim 26 wherein said one or more tubes have ends of wider board toprevent capillary loss of the viscous fluid.
 28. A filter as claimed inclaim 25 wherein the vents communicate with one or more channels locatedin the periphery of the filter and have viscous fluid disposed therein.29. A filter as claimed in claim 26 or claim 28 wherein removal meansare provided around the fluid exit end of the channels or tubes toassist the removal of viscous fluid.
 30. A filter as claimed in claim 29wherein the removal means comprise slits, channels or tubes.
 31. Afilter as claimed in claim 29 wherein the removal means comprises anouter concentric channel or tube.
 32. A filter as claimed in claim 31wherein the tube or tubes are conical.
 33. A filter as claimed in claim20 wherein the viscous fluid has a viscosity between 0.01 Poise (0.01Stokes) and 1000 Poise (1000 Stokes).
 34. A filter as claimed in claim20 wherein the viscous fluid is plastic deformable under load withoutreturning to its original shape after the load is removed.
 35. A filteras claimed in claim 20 wherein the ventilation means is biodegradable.